I'm considering buying a lot of ptfe capacitors for fooling around with amps and circuits. Can get them in large bulk for around 10 cents each between 0.015 and 0.47 uF. Is there a point to having such a variety just for the sake of perfectly duplicating circuits or is it best to work out a favorite value and stick to it. can also get 6.8 uF for when I want the cap to be ' transparent'?
Any other value ranges to look into?
Any other value ranges to look into?
It all depends on what resistance follows, and where you want to put the LF roll-off (open-loop) or LF poles (closed-loop). The idea of 'favourite value' is meaningless. How long is a piece of string? Values I have seen go from 2nF (old radio which didn't do bass!) to 0.68uF. If you want to buy some for playing with then 10nF, 22, 47, 100, 220nF would be a good place to start because you would be within 50% of most reasonable values.
6.8uF would not necessarily be 'transparent'. It would be big, and might increase hum pickup or RF interference. It could even lead to HF instability, simply because of its physical size. Bigger is not necessarily better!
6.8uF would not necessarily be 'transparent'. It would be big, and might increase hum pickup or RF interference. It could even lead to HF instability, simply because of its physical size. Bigger is not necessarily better!
That short list is actually somewhat what I already had in mind, I was thinking the 0.01-0.33 uF range and the 0.1 to 0.47 uF range. Was mostly curious about the 1 to 6 uF range as my current preamp circuit I use has 3.3 uf cap coupling it to the driver tube, I assumed the large value was so that one could adjust cutoff etc based on the dual triodes and the interstage didn't affect anything
You might need 3.3uF if you have a very low grid leak, or you want to listen to earthquakes (and have speakers and ears which go down that far!).
As a coupling capacitor for a valve circuit it seems rather large, yes. If the following grid leak is 100K then your LF rolloff is at 0.5Hz.
Teflon/PTFE caps at .10 is a bargin....
I'm always asked for .01, .022, .047, and .1Uf
customers still play around and when I'm out of stock I
sell .03 and .068. However I do not have any Teflon caps in stock
What voltage are these caps?
Steve @ Apex Jr
I'm always asked for .01, .022, .047, and .1Uf
customers still play around and when I'm out of stock I
sell .03 and .068. However I do not have any Teflon caps in stock
What voltage are these caps?
Steve @ Apex Jr
E6 range from 10pF to 1000pF in both NP0 ceramic and silvered mica.
E6 range from 100pF to 10nF in metallised polypropylene film.
E6 range from 1nF to 470nF in metallised polyester film.
E6 range from 100pF to 10nF in metallised polypropylene film.
E6 range from 1nF to 470nF in metallised polyester film.
Im sorry, there not ptfe, they are polymer caps, doesnt affect the context of this discussion however. I must have remembered looking at the teflon value range when I wrote about it
I bought 50 pcs of 0.33uF caps several years ago for coupling job in tube amps, and I'm quite happy with that value, never really needed something else. Last month bought another 30 pcs of the same value, and I hope to be happy again for some time.
In general I'd say that 0.22 or 0.33 or 0.47uF is a pretty universal choice.
In general I'd say that 0.22 or 0.33 or 0.47uF is a pretty universal choice.
So unless I'm looking to roll off relatively high freq, over 0.1 uF is a good general point to design around going by my quick calculations
.01, .022, .047, .22, .47 .1 , and 1 uf all 400V-630V but not 1000V
anything above 1, use a electrolytic and bypass it with a .01-.1 cap or parallel caps
anything above 1, use a electrolytic and bypass it with a .01-.1 cap or parallel caps
Many dielectrics are polymers (polymer is a broad class of substances, not a particular type of substance) so which particular polymer are they? Some are better than others, although opinions vary, but to some extent it depends on how they are used in the circuit.
there PETP capacitors, soviet NOS, i ordered for values to start off with:
.1, .22, .47, 1, 2 uF, got the whole bunch for $60 shipped
i was considering sub 0.1uF but i figure ill buy those separately as needed
there inexpensive and sold in bulk, so even if they are inferior to my k40y-9's they will be good for experimenting with circuits i think
.1, .22, .47, 1, 2 uF, got the whole bunch for $60 shipped
i was considering sub 0.1uF but i figure ill buy those separately as needed
there inexpensive and sold in bulk, so even if they are inferior to my k40y-9's they will be good for experimenting with circuits i think
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For poly caps, I like Orange Drop caps, Solen, and Dayton film and foil poly.
sometimes, I like to use motor start/run caps for coupling.
but for me: any low esr, and low inductance cap will do.
sometimes, I like to use motor start/run caps for coupling.
but for me: any low esr, and low inductance cap will do.
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